It is well known that in primates, such as humans and gorillas, the Y chromosome of sperm tends to fluoresce to a special brightness when stained with a dye such as quinicrine or quinicrine mustard whereas the X chromosome of sperm will not fluoresce. It is also known that the sperm of most other animals will not normally be subject to this selective staining unless a cell wall diffusion material or agent, such as an appropriate enzyme or chemical, is used to facilitate passage through the cell wall or cell membrane so that the dye can enter the cell. A commercially available chemical for this purpose is dimethylsulfoxide. It is also known that by adding papaya protease to the sperm of horses and bulls, the cell membrane can be penetrated by the dye so that selective identification of the X and Y chromosomes can be accomplished under a microscope. A disclosure of this technique is found in U.S. Pat. No. 4,155,831 entitled "Thermal Convection Counter Streaming Sedimentation and Forced Convection Galvanization Method and Apparatus for Controlling the Sex of Mammalian Offspring", issued May 22, 1979 to Bhairab C. Bhattacharya. Such a process has been used in the prior art to determine the success ratio in separating X and Y sperm by other known methods.
A device for identifying and then separating live blood cells from dead blood cells is disclosed in U.S. Pat. No. 3,791,517 for "Digital Fluid Amplifier Particle Sorter", issued Feb. 12, 1974 to Mitchell Friedman. It is suggested in this patent that the separating of the particles may be done, if desired, by use of selective fluorescent radiation responses from the particles.
However, no known way has been suggested in the prior art for staining Y chromosomes so that they fluoresce and using the fluorescence as a means of separating the X chromosomes into one container and the Y chromosomes into another container. This is of particular significance in cattle breeding wherein it is desired to have a large number of female offspring with dairy cattle and a large number of male offspring with beef cattle. Also, such a separating technique, if available, would have wide application in any situation where predetermination of the sex of the offspring would be desirable.
The other known methods of separation depend on existing physical differences between sperm containing either the X or Y chromosome. The difference includes slightly larger size and heavier weight of the sperm containing the X chromosome, generally higher velocity of movement of the Y chromosome containing sperm, and an apparent dense negative electrical surface charge on the X chromosome. However, the methods of separation of sperm utilizing these physical properties have, for the most part, been only partially successful with separation percentages ranging from 60% to 80%. Thus, there is a very great need for a method of sperm separation which is virtually 100% accurate and which can be done very rapidly. Furthermore, in order to accomplish separation, it is necessary to maintain or get the semen which has been collected in a fluid non-coagulated condition before the separation can be accomplished.